In two fluid, parallel plate heat exchangers constructed of metal parts, typically a hot fluid flows between first and second adjacent plates and transfers heat to the plates. This will be referred to as the hot passageway. A cold passageway, transverse or parallel to the hot passageway is constructed on the opposite side of the second plate. A second and cooler fluid flows in this passageway. These hot and cold passageways can be alternated to form a stacked array. Metal fins are provided between adjacent plates to assist the transfer of heat from the fluid in the hot passageway through the plate to the cold fluid in the second passageway,. These fins are bonded to the plates providing extended heat transfer area and sufficient structural support to provide pressure containment of the fluids. To minimize flow blockage, the fins are disposed in parallel with the fluid flow and define a flow path with minimum additional flow resistance. In addition, the thickness and number of fins is such to provide a maximum heat transfer area in contact with the fluid. A thin fin satisfies these requirements and many different detailed geometry's are used to best satisfy the specific requirements of any given design problem.
Heretofore composite materials have been considered unavailable for these compact parallel plate heat exchangers. It has been considered impossible to achieve a composite fin which is sufficiently thin, sufficiently conductive and could be formed into an acceptable shape to be effective in transferring heat between the two fluids. Also, the fins must exhibit sufficient strength to support the stacked construction and provide pressure containment of the fluids.